Friday, 15 October 2010

Thanks to better brain imaging and biological insights, we're closing in on the neurons of consciousness and the subtleties of our mental machinery

Cognitive control

Towards the seat of consciousness
The question "what is consciousness?" represents one of the great frontiers of contemporary science. Thanks to studies of humans and animals, we now know that it is a subtly nuanced state whose nature and intensity varies according to the brain's intrinsic level of activity, its chemical microclimate and the information it receives from outside.
By exploiting the normal vicissitudes of waking, sleeping and dreaming states, we are now beginning to explore how consciousness is expressed and controlled. For example, I have been involved in studies comparing brain activation in REM sleep with that in lucid-dreaming states, in which we retain much executive brain function. They seem to confirm the central importance of one specific area of the frontal brain - the dorsolateral prefrontal cortex - in regulating many key aspects of consciousness, including attention, decision-making and voluntary action.
A combination of imaging techniques, judicious measures of subjective experience and detailed cellular and molecular-level studies will continue to deepen our understanding of our cognitive command centres in the coming years. With them we hope to crack the puzzle of consciousness, and perhaps correct the dysfunctional states of the brain we now call mental illness. Allan Hobson
Allan Hobson is emeritus professor of psychiatry at Harvard Medical School in Cambridge, Massachusetts

The connectome

Mental maps              
Understanding the routes by which populations of brain cells share information would be a major step towards understanding how our brains function. But although we can infer individual connections, we have no basic wiring diagram of the human brain.
This is hardly surprising. The brain contains approximately 100 billion neurons, and a single neuron may connect to 10,000 others. Yet emerging techniques mean we are now making headway in this daunting task.
Using electron microscopes, for example, we can probe animal brains neuron-by-neuron, connection-by-connection, in the hope of discovering characteristic circuits that repeat themselves throughout the brain. From a wider perspective, brain imaging technologies can map the brain's highways - large "cables" consisting of many thousands of connections between distinct brain regions.
The US National Institutes of Health has begun to fund a major effort, theHuman Connectome Project, to generate a comprehensive map of large-scale brain connections in humans. Following its directions, we might arrive at a better understanding of how the brain's regions interact to produce behaviour.Tim Behrens
Tim Behrens is a neuroscientist at the University of Oxford 
The key to how we learn and think - possibly...
The saying "monkey see, monkey do" couldn't be more true. Thanks to "mirror" neurons that fire not only when we perform an action ourselves but also when we see others perform it, our primate brains subconsciously mimic every behaviour they ever witness.
That's the theory, at least. Mirror neurons were first discovered in macaques in the 1990s, and brain scans using functional MRI had hinted that they exist in humans too. But it wasn't until May this year that researchers measured the firing of mirror neurons in humans directly, using electrodes implanted in the brains of epileptic patients awaiting surgery (Current Biology, vol 20, p 750).
While proponents of the power of mirror neurons claim they explain everything from empathy and compassion to a penchant for porn, their exact significance remains controversial. The next few years will see us homing in on what exactly they can and cannot explain about human cognition.

Top-down processing

Our past determines our present           
The human eye is a camera that faithfully records everything in front of us, passing the information through the brain's visual processor before it pops out as a conscious experience.
This "bottom-up" process represents the textbook view. In truth, we are realising that our experience is closer to a form of augmented reality, in which our brain redraws what it sees to best fit our expectations and memories.
The same goes for our other senses, and the growing suspicion is that kinks in this system of "top-down processing" might shed light on neurological disorders such as schizophrenia, autism and dyslexia. Whether or not that turns out to be the case, this idea is radically changing our view of how our past influences our here and now.

Neuronal recycling

Culture is a parasite           
The architecture of our brains far predates writing, religion and art. So how come we acquire these cultural traits and abilities with such ease?
The standard answer is that our big, plastic brains have a uniquely flexible and generalised learning capacity. But is that true? The human brain is not homogeneous, after all, but organised into specialised areas. Moreover, brain imaging reveals that abilities such as reading and mathematics have distinct "neuronal niches"; they too are confined to specific brain circuits

That is compelling evidence for an idea known as neuronal recycling: that our cultural abilities invaded and parasitised brain circuits originally dedicated to evolutionarily older, but related functions. Reading, for example, seems to occupy circuits sensitive to complex shapes and with good connections to areas dealing with language (Reading in the Brain, Viking, 2009). If correct, it is our brains shape our culture, rather than our culture our brains. Human ingenuity is not unlimited, but fundamentally constrained by neural architecture.

Nootropics

Food for thought           
You've got a big report to file, and the clock is ticking. If only you could concentrate harder, recall facts and figures more effectively, or just shake off that feeling of fatigue after yesterday's late night.
Soon a brain boost might follow a visit to your local pharmacy. Psychostimulant drugs such as Ritalin and Adderall, prescribed to treat attention-deficit hyperactivity disorder, and Aricept, used as a treatment for Alzheimer's disease, have been shown to improve concentration and recall in healthy people, too.
Such drugs are not currently available without a prescription, but some researchers say they should be. Multiply that extra brain power by the 7 billion members of the human race, they say, and the benefits to society and the pursuit of knowledge would soon start to add up. But is a race of drugged-up super-brains what we really want to be? Food for thought indeed.

Friday, 8 October 2010


Humans know less than they 
think...
Shock!
IF NEW satellite data can be trusted, changes in solar activity warmed the Earth when they should have cooled it.


Joanna Haigh of Imperial College London studied satellite measurements of solar radiation between 2004 and 2007, when overall solar activity was in decline. The sun puts out less energy when its activity is low, but different types of radiation vary to different degrees. Until now, this had been poorly studied.
Haigh's measurements showed that visible radiation increased between 2004 and 2007, when it was expected to decrease, and ultraviolet radiation dropped four times as much as predicted.
Haigh then plugged her data into an atmospheric model to calculate how the patterns affected energy filtering through the atmosphere. Previous studies have shown that Earth is normally cooler during solar minima.Yet the model suggested that more solar energy reached the planet's surface during the period, warming it by about 0.05 °C (Nature, DOI: 10.1038/nature09426).
The effect is slight, but it could call into question our understanding of the sun's subtle effects on climate. Or could it? Stefan Brönnimann of the University of Bern in Switzerland says Haigh's study shows the importance of looking at radiation changes in detail but cautions that the results could be a one-off. He points out that the sun's most recent cycle is known to have been atypicalMovie Camera

First frictionless superfluid molecules created


CHILL them enough and some atoms creep up walls or stay still while the bowl they sit in rotates, thanks to a quantum effect called superfluidity. Now molecules have got in on the act.

Superfluidity is a bizarre consequence of quantum mechanics. Cool helium atoms close to absolute zero and they start behaving as a single quantum object rather than a group of individual atoms. At this temperature, the friction that normally exists between atoms, and between atoms and other objects, vanishes, creating what is known as a superfluid.
To see if molecules could be made superfluid, Robert McKellar of the National Research Council of Canada in Ottawa and colleagues turned to hydrogen, which exists as pairs of atoms. The team created a compressed mixture of hydrogen and carbon dioxide gas and shot it through a nozzle at supersonic speeds. Once released, the molecules spread apart, cooling and arranging themselves so that each CO2 molecule sat at the centre of a cluster of up to 20 hydrogens.
To test for superfluidity, the team shone an infrared laser at the clusters at wavelengths that CO2, but not hydrogen, can absorb. This set only the CO2molecules vibrating. Under normal conditions this movement would be slowed down due to friction between the moving CO2 molecules and the surrounding hydrogen. But the researchers found that for clusters of 12 hydrogen molecules, the hydrogen barely impeded the motion of the CO2.
They conclude that these hydrogen clusters are 85 per cent superfluid (Physical Review LettersDOI: 10.1103/PhysRevLett.105.133401).
As hydrogen is only the second element known to form a superfluid, McKellar says the experiment could be useful for disentangling general qualities of superfluids.
Superfluid molecules might also be used as "nano-fridges", which surround and cool individual protein molecules. Superfluid helium atoms are already used for this but, unlike atoms, molecules can bend and stretch, which might present new ways to manipulate the cooled proteins.